Structures supported on ice, such as ice fishing shelters supported on a frozen body of water, commonly include a heated shelter having a floor above the ice, and openings through the floor to access the ice and body of water below. Typically, holes are cut through the ice using a circular auger having a predetermined diameter, and the openings through the floor may be of slightly larger size to access the hole. Covers are often placed over the openings through the floor when not in use, and in some cases, the openings may have a perimeter fitted with a frame, such as a circular-shaped flange, engageable with the cover. Various structures have been used between the floor and ice surface, such as rigid tubes made of polyvinylchloride (PVC).